How the carboxyl group different from hydroxyl group

The carboxyl group (-COOH) and the hydroxyl group (-OH) are both functional groups commonly found in organic molecules, but they differ in their chemical properties and structures:

1. Chemical Composition:

   • The carboxyl group consists of a carbon atom doubly bonded to an oxygen atom (carbonyl group, -C=O) and singly bonded to a hydroxyl group (-OH). It is represented as -COOH.
   • The hydroxyl group consists of an oxygen atom singly bonded to a hydrogen atom. It is represented as -OH.

2. Acidity:

   • The carboxyl group is acidic because it can donate a proton (H+) from the hydroxyl group, resulting in the formation of a carboxylate anion (-COO^-).
   • The hydroxyl group is not acidic under normal physiological conditions and does not readily donate protons.

3. Functional Group Classification:

   • The carboxyl group is classified as a carboxylic acid functional group due to its acidic properties.
   • The hydroxyl group is classified as an alcohol functional group.

4. Polarity:

   • Both the carboxyl group and the hydroxyl group contain polar bonds due to differences in electronegativity between the atoms involved (oxygen and hydrogen). However, the polarity of the carboxyl group is influenced by the presence of the carbonyl group, making it more polar than the hydroxyl group.

5. Structural Role:

   • The carboxyl group is commonly found at the terminus of carboxylic acids and amino acids. It imparts acidic properties to these molecules and participates in various chemical reactions, including esterification, amidation, and decarboxylation.
   • The hydroxyl group is present in alcohols, phenols, and carbohydrates. It contributes to the solubility of alcohols in water and can form hydrogen bonds with other molecules.

Overall, while both the carboxyl group and the hydroxyl group contain oxygen atoms bonded to hydrogen atoms, they differ in their acidity, chemical properties, and structural roles. The carboxyl group's acidic nature and its presence in carboxylic acids make it distinct from the hydroxyl group, which is more commonly found in alcohols and phenols.